The invention relates to an intake system for an internal combustion engine, which comprises a conventional air filter for filtering the air and a membrane that is preferentially permeable to oxygen molecules.
The use of membranes for oxygen enrichment of the combustion air is known in the art. Commercial designations for known materials used for oxygen enrichment of the air include, for example, silicon and polysulfone. Published German patent application no. DE 197 10 840 A1 proposes such a system. According to the single figure of this document, this system comprises an intake tract in which an air filter 22 is arranged. In addition, there is another housing, which is provided with a membrane that is preferentially permeable to oxygen molecules. This housing is also connected with the intake tract so as to create a parallel connection of the described air filter 22 and membrane 32. Depending on the position of throttle valves 24 and 34, the combustion air can be enriched with oxygen.
Such an enrichment of the intake air supplied to the engine increases the temperature of the exhaust gas and thus shortens the catalyst initiation time, i.e., the time that passes before the catalyst reaches its operating temperature and thus develops its full effect. In addition, fuel conversion in the engine is improved. This makes it possible to reduce the emission of carbon monoxide and hydrocarbons in the exhaust gas. The nitrogen content of the combustion gases is also reduced, so that fewer nitrogen oxides are generated. Thus, environmental pollution due to the exhaust gasses of the internal combustion engine can be decreased overall.
The use of membrane technology to enrich the combustion air with oxygen, however, creates additional component costs for the intake system. Furthermore, it increases the overall space requirement within the vehicle. The total volume available in modern motor vehicles is limited, however. Moreover, at the same time there is great interest in economically efficient solutions.
Accordingly, it is an object of the invention to provide an improved intake system for an internal combustion engine which can produce an intake air stream with an enriched oxygen content.
Another object of the invention is to provide an intake system for an internal combustion engine, which comprises an air filter and a membrane that is preferentially permeable to oxygen molecules.
A further object of the invention is to provide an intake system for an internal combustion engine with a membrane that is preferentially permeable to oxygen and which is inexpensive to manufacture and economical to operate.
These and other objects are achieved in accordance with the present invention by providing an intake system for an internal combustion engine, comprising an intake passage that connects an intake opening with at least one cylinder inlet of the internal combustion engine; an air filter housing arranged as part of the intake passage; a filter insert arranged in the air filter housing such that a flow of air drawn through the intake passage will pass through the filter insert; and a membrane preferentially permeable to oxygen molecules, the membrane being arranged in the intake passage such that a flow of air drawn through the intake passage will pass through the membrane; wherein the membrane is integrated into the air filter housing and forms part of a wall of the air filter housing.
The intake system according to the invention comprises an intake passage in which at least one air filter and a membrane preferentially permeable to oxygen molecules are accommodated. The term intake passage should be understood in a broad sense as a structure that forms the intake path from an intake opening up to at least one cylinder inlet of the internal combustion engine. Additional components that are essential to the functioning of the internal combustion engine are accommodated in this intake path. For instance, a throttle valve and an intake manifold comprising a plenum and at least one intake port per cylinder form part of the intake passage.
According to the invention, the membrane is built into the air filter housing. This integration saves space as well as weight of the components of the intake system. At the same time, a corresponding configuration can save production costs to make the proposed solution more economically efficient.
In accordance with a further embodiment of the invention, the membrane is arranged parallel to the filter insert in relation to the airflow. This variant is particularly simple to realize if the membrane is accommodated within the air filter housing. The parallel flow consistently ensures a minimum flow of combustion air through the filter insert.
One advantageous embodiment is obtained if the membrane forms part of the air filter housing. This creates an especially space saving variant since the surfaces of the filter housing are available in any case. They can then be used to enrich the combustion air with oxygen. Due to the pressure drop across the membrane used, a large membrane surface is necessary to enrich the air as much as possible with oxygen.
It is advantageous to provide the membrane, which forms a portion of the wall of the air filter housing, with a shield. This shield protects the membrane against contaminants, e.g., against road spray that may enter the engine compartment. Contamination of the membrane would impair its function and thus reduce its separation efficiency. The shield may, for example, comprise a cover, which is provided in the engine compartment for reasons of appearance or noise dampening. These covers are increasingly attached directly to the air filter housing so that their shielding effect can simultaneously be used to protect the membrane.
An alternative measure to reduce the operating costs of the internal combustion engine or to improve the function of the intake system is to arrange the membrane behind the air filter as seen in flow direction of the intake air. In this way, the membrane is contacted only by clean air that has been filtered by the filter insert, so that contamination of the membrane can be largely avoided. Replacing the membrane is therefore unnecessary. To install the membrane, space must be provided within the intake system on the clean air side. This space can, in particular, also be located within the air filter housing. This makes it possible to obtain the above-described advantages regarding space utilization.
According to a further development of the integration concept, the intake manifold for the internal combustion engine is also integrated with the housing for the filter insert. This results in a particularly compact construction. The separating wall between the air filter housing parts and the manifold can advantageously be used to accommodate the membrane. This makes it possible to utilize a larger area for accommodating the membranes without increasing the overall volume of the intake system.
The membrane does not need to be configured as a foil, although a foil is particularly easy to integrate into parts of the wall of the filter housing. One measure to increase the effective membrane surface, however, is to use hollow fiber membranes. The ends of these membranes can, for instance, be integrally molded into a wall part of the housing, so that a space saving geometry is again obtained.
It is advantageous to arrange a throttling member parallel to the membrane in the intake passage. This function can be assumed, for instance, by the throttle valve, which is in any case provided in the intake tract. If this throttle valve is arranged parallel to the membrane, the intake air stream can be throttled only to a degree where the main intake airflow guided through the filter insert is completely shut off. The secondary flow that is drawn through the membrane is always available in the intake tract. Thus the amount of air sucked through the membrane must be less than or equal to the amount of air required during idling. In this manner, the largest possible amount of oxygen-enriched air is always made available.
It is also possible, however, to arrange a throttling member in the secondary airstream of the intake passage, which is connected in series with the membrane. In conjunction with the throttle valve in the intake passage, the air supply to the internal combustion engine can thus be completely blocked. In addition, the air amount drawn in through the membrane can thereby be regulated, making it possible also to influence the degree of oxygen enrichment of the combustion air. In this embodiment of the intake system, it is possible to use a membrane that allows a greater amount of air to pass through than is required during idling.
To be able to control the oxygen content, a sensor may be provided in the intake passage, which determines not only the amount of air being passed through but also its oxygen content. These measured values can be used to determine the amount of oxygen supplied to the internal combustion engine and to control that amount through corresponding adjustment of the throttling members.
These and other features of preferred embodiments of the invention, in addition to being described in the specification and drawings, are also set forth in the claims. The individual features may be implemented either alone or in combination in embodiments of the invention or in other fields of use and may represent advantageous, separately protectable embodiments, for which protection is hereby claimed.